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e30prideTN
02-16-2007, 06:19 PM
I've heard robs knocking before on a jeep, but if I can remember correctly, it does it at idle right?

I can hear a subtle 'knocking' noise while I accelerate; gets louder the harder I push it. Any suggestions as what to check?

I haven't talked to my brother yet, but I'm going to get him to rebuild my spare I motor and let him take my eta motor when we swap it out. I don't want to have to repair anything if I'm going to be swapping it out.

superj
03-25-2007, 10:06 AM
rod knock can be heard anytime the engine is running but is alot more noticable at acceleration or under any kind of load. try running super unleaded because maybe you are getting preignition knock instead of rod knock.

to check if it is rod knock, unplug a spark plug wire, one at a time and rev the engine. if the knock disappears then it is that cylinder with a bad bearing.

rereading your description, i think you jsut need to run premium gas. did you put in a chip lately?

87-325iC
03-25-2007, 10:57 AM
so is rod knock just a loose wobbly bearing on the piston or crank?

what causes this to occur, or to get to the point where it makes sounds..?

Capman87
03-25-2007, 12:39 PM
Rod knock can be a couple of things, First off we should start with the rod bearings on the crank shaft sides.
Sometimes if you have detonation or pinging, the force of detonation can cause a hole to be blown into the piston destroying a lot of things, but sometimes it will not ruin the piston however it can create a "squished" spot (or side) on the bearing.
Now with the bearing squished the gap between bearing and crankshaft are obviously going to be larger, this will cause play in the rod bearing allowing it to knock as it moves from tdc down or bdc up.
Rod knock can also be caused by loose cap bolts.
The other cause of rod knock can be from the wrist pin in the piston is loose in the top of the rod. Rod knock is not always caused by detonation or pinging eather, over boost or hydrolocking or even normal engine wear could cause it if the motor is not properly maintained.
Are you positive its a rod knock and not a piston slap?

superj
03-25-2007, 02:52 PM
yup, could be piston slap also.

superj
03-25-2007, 02:58 PM
if it was rod knocking, they usually don't knock for to long before they go through something or destroy the bearing so much that it hurts you to drive the car and hear it making that noise.

when my ghia started knocking it was so horrible that i turned it off as soon as i heard it and it still required the crank to be turned and all new oversized bearings plus a connecting rod or two.

nomade30
03-25-2007, 03:40 PM
umm also are you certain it's come from the engine bay area?

g323
07-26-2009, 06:31 PM
rod knock can be heard anytime the engine is running but is alot more noticable at acceleration or under any kind of load. try running super unleaded because maybe you are getting preignition knock instead of rod knock.

to check if it is rod knock, unplug a spark plug wire, one at a time and rev the engine. if the knock disappears then it is that cylinder with a bad bearing.

rereading your description, i think you jsut need to run premium gas. did you put in a chip lately?

I tried removing one spark plug wire at a time and the tapping didnt stop - Can I drop the oil pan and check for up/down play? would that work? What about removing 2 spark plugs at a time? if 2 bearings are bad would they be right next to each other?

jonmon6691
07-26-2009, 09:31 PM
I hope its not rod knock dude, that's how I lost my last car. Its not likely that two bearings would be going out at the same time, has the oil been critically low recently? If you're going to take the pan off and check them, you might as well replace 'em.

superj
07-27-2009, 08:54 PM
is it lifter tap, g323?

JohnyEndo
07-27-2009, 09:15 PM
if it was piston slap it would go away soon as the engine got up to temp right? so he doesn't have that.

could very well be rod knock from his descriptions.

colin86325
07-27-2009, 09:53 PM
With a fully warmed engine, what happens when you accelerate [in a safe area--don't want to get rear-ended] to say 60mph next to a wall or cement divider and then take your foot suddenly off the gas while leaving the car in gear? With your windows down, is the knock there or even more pronounced as the rpms fall? Let the rpms fall as far as you can [again watch the rear view mirror so you don't get hit] until about 1k rpm.
Rod bearings will usually make noise under these conditions. Having a nice cement wall or tunnel makes engine noises more audible to the driver.

Also drain your oil into something flat that you can inspect as it's draining. You're looking for gold-colored flecks or sparkles under adequate lighting. Many people even cut apart their oil filters and look for metal on the filter media. Very messy work though.

g323
07-27-2009, 10:27 PM
Superj: what is lifter tap

Colin: I dont want to drive it while it's tapping, ive driven it 1 mile max while testing - When I let off the gas pedal quickly it does tap while it decelerates yes, at the same rate i would say.

Also, I lost a core plug recently when it rusted through, while changing it curbside I accidently moved the car up on to the curb - with the oil filter off!!!! made a huge mess. - Could this have done specific damage?

JohnyEndo
07-27-2009, 11:53 PM
lifter tap is what you get in the head between the rockers and the valves. the m20 needs periodic adjustment since we dont have hydrolic lifters, but eccentrics.

g323
07-28-2009, 12:14 AM
Ooooo Lifter tap - yes, I've done multiple valve adjustments; here is the main thread on my issue

http://www.e30tech.com/forum/showthread.php?t=79535&page=2

colin86325
07-28-2009, 12:37 AM
Inspect your oil as you drain it. You could drain it prematurely save an engine.

g323
07-28-2009, 01:15 AM
If I drain it I will probably drop the oil pan also and feel all the rods for play. Your'e saying I should look for golden flakes or sparkle? If I pull the dipstick on the engine warm would I see the same thing?

Also - To drop the oil pan need I jack the motor - or is there enough clearnace?

jonmon6691
07-28-2009, 01:25 AM
If I drain it I will probably drop the oil pan also and feel all the rods for play. Your'e saying I should look for golden flakes or sparkle? If I pull the dipstick on the engine warm would I see the same thing?

Also - To drop the oil pan need I jack the motor - or is there enough clearnace?

Definitely jack it up (but do it right ;)), taking the oil pan off isn't as simple as it sounds.

g323
07-28-2009, 01:37 AM
haha - I feel like there is a secret here!?! what is the secret? How do I do it "right"? What makes it such a complex task?

Thank you!

jonmon6691
07-28-2009, 02:47 AM
haha - I feel like there is a secret here!?! what is the secret? How do I do it "right"? What makes it such a complex task?

Thank you!

Do you have a repair manual? It will tell you everything you need to know, and what makes it complicated is other parts that need to be removed first, things you should be careful about, tricks that make it easier, bolt torque specs and sequences.

g323
07-28-2009, 06:02 PM
I have a bunch of repair manuals for my car - they all require you to remove the engine before doing any motor work.

jonmon6691
07-28-2009, 07:18 PM
Haha, you don't need to go that far. Search the forum (There's a link on the horizontal menu bar on every page that says "Search") Just type in "remove oil pan" or something to that effect. There is also a sub forum that is all about how-to's, check that too.

Ranger
07-30-2009, 10:09 AM
For $60 you can get a device from Harbor Freight that will lift your engine a couple inches. This is a better approach then a normal engine hoist, in this case, because a hoist's legs would go underneath the motor making it a pita to work down there.

With the engine up a couple inches you can easily remove your oilpan and screw with your rod bearings.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=96524